I think this is still up or debate. While this did appear to bring down the newly crowned Alicorn Twilight in the episode, her actual mark hasn't changed. But then again its possible the animators kept her mark the same because they were trying to make sure they weren't giving away a spoiler of a new main character.

I find this a possibility, as Nightmare Moon Luna's mark was different and seeing in this episode the Mane Six have theirs switched (plus the fact that Twilight's dress as a princess is hiding her mark.) Twilight's mark could have evolved during the process.

Well nevermind then Man, I thought for a moment that I was going to miss the episode since I usually sleep in on Friday. Never seem to be able to keep myself awake that day >=? And I definitely don't want to miss this!